Online social media services, such as social networking sites, search engines, news aggregators, blogs, and the like provide a rich environment for users to comment on events of interest and communicate with other users. Social media content items authored by users of social networking systems often include references to events that appear in time based media such as television shows, news reports, sporting events, movies, concert performances, and the like. However, although the content items can sometimes refer to the time-based media, the social media content items themselves typically are isolated from the events and time-based media that those content items refer to.